Project summary/Abstract Optical imaging techniques have demonstrated potential to delineate tumor margins in vivo during surgery as they can rapidly characterize structural, biochemical or functional properties of tissue. Implementation in clinical practice demands rapid visualization and augmentation of imaging data but is often limited by the difficulty in dynamic registration, slow image reconstruction, lack of real- time ability or the need for contrast agents. The goal of this proposal is to implement the recently released Microsoft HoloLens with fiber-based imaging techniques to dynamically augment tissue characteristics directly on the interrogated area in the surgeon?s field of view. The specific aims of this proposal are as follows: (1) To realize a prototype of the augmented reality visualization platform and to combine it with our fluorescence lifetime imaging (FLIm) system, implement a user interface for a convenient interaction with the device. (2) To evaluate and optimize the scanning resolution and the registration precision using fluorescence phantoms and demonstrate the system in vivo for ten patients undergoing lumpectomy surgery. A current pilot study has demonstrated the potential of FLIm to localize tumor margins on excised breast specimen. The acquired in vivo data will help to systematically analyze differences between ex vivo and in vivo fluorescence decay signatures and provide initial data for a large-scale study that will be necessary to delineate tumor margins in vivo. The innovation of this proposal is that it will realize an augmented reality visualization platform for FLIm and other fiber based optical imaging modalities providing dynamic (continuous) augmentation of tissue properties directly on the interrogated area (surgeon?s field of view) in real-time without requiring the injection of contrast agents. The successful completion of this work has consequently the potential for significant impact in the field of surgical navigation.